If it's rough to cycle, I'd be worried about lug set-back, especially with a higher pressure round compared to its original.
I'm sure your gunsmith is better qualified than I am, but it's the first thing I thought of.
Cycle could mean anything. OP, ought to give a little more detailed explanation if he wants anything resembling useful advice.
Hard to open after firing? Hard to feed a cartridge out of the magazine into the chamber?
I'm guessing the later and if so, would suspect that the 7mm-08 is causing feeding issues. Why someone would covert from 7x57 to 7mm-08 is beyond me but it happens. Could have been a shot out barrel.
